Have you ever finished working on an assignment or project and felt physically exhausted?

As it turns out, your brain burns through calories at a pretty consistent rate: 1.5 calories a minute. That’s 90 calories an hour, comparable to running a mile at 6 miles per hour.

How, exactly, does thinking burn calories though?

Your brain uses a process of firing neurons to send signals to parts of the body, and those neurons need a lot of fuel in order to function. “The more energy an area of the brain wants, the more glucose that part of the brain will break down,” explains neurologist Harry Chugani of the Children’s Hospital of Michigan. “If you’re thinking really hard and really struggling with your thoughts, the neurons in the frontal lobes of your brain will be burning a lot more glucose.”

That’s a lot to think about, try not to break a sweat taking all of that delicious information in.